Heretofore, no system of instrumentation has been developed which enables a medical professional such as a surgeon to accurately apply specific required measured pressure upon the surgically prepared patella construct to maximize the highest success of the bone cement bond relative to the resurfaced natural patella and the artificial patella replacement and also, indicating known pressure to give mindful consideration to minimize the risk of creating micro-fractures in the host patella.
The typical known art of surgically resurfacing the natural patella, when necessary to accept an artificial patella prosthesis, requires the patella to be everted and held in a position allowing the surgeon to have access to the articulating surface which normally articulates within the intercondylar notch between the femoral condyles.
The natural patella is first measured, establishing its exact thickness, after which the surgeon resects the appropriate thickness of the posterior portion of the natural patella, and then prepares the surface to receive the artificial patella prosthesis. A patella trial replicating the actual implant to be installed is placed upon the prepared patella surface to confirm proper fit and thickness of the patella construct that establishes proper ligamentus tension for optimum stability and range of motion whereupon, a bonding agent (e.g., bone cement) is prepared. In the typical known handling of the bone cement, there is an exact science of measured polymer (e.g., powder) and monomer (e.g., liquid) packaged sterile in their individual respective states delivered into a sterile field placed into and enclosed in a sterile container whereupon measured vacuum force is applied and a measured time of thorough mixing is conducted. The properties are handled under strict scrutiny and respectful disciplines. When the vacuum is released, the top of the sterile container can be removed, giving access to the bone cement, whereupon it is examined to confirm that it is in the proper state to be applied. Precautions are generally taken to create the bone cement and bring it into a proper stable useable product, whereby it can be applied in order to successfully bond the aforementioned surfaces. At this juncture, and in the past art, the typical known patella clamp is applied and a disruption to sound science and respect to mechanical properties of the bone cement occurs, putting the surgeon in an unfortunate place of having to use inadequate instrumentation to carry out this process in respectful consideration of all parameters involved.
In the past, it is known to apply a clamp to the patella construct (which consists of the surgically resurfaced posterior aspect of natural patella prepared to receive an artificial patella replacement paired with the bonding agent bone cement). However, methods and devices for applying the pressure have not been controlled and have resulted in the application of an arbitrary and unknown pressure upon the patella construct until the bone cement is fully cured. As such, less than satisfactory results can occur.
Measured pressure upon the patella construct is a paramount consideration to the mechanical properties, scientific quantitation and increased long-term success of the bonding integrity of the bone cement. Heretofore, no patella clamp has existed for general surgical use which takes into account all the parameters and dynamics taking place within the patella construct as it relates to all surfaces involved and the scientific and mechanical properties of the bonding agent bone cement during installation, as well as, the potential of excessive unknown pressure upon the host patella creating micro fractures.
In various aspects, the present invention enables the medical professional (i.e., surgeon) to accurately apply positive linear directional control and known pressure upon the patella construct throughout the process to the cure state of the bone cement. After the initial proper pressure is established upon the patella construct, certain variables can come into play affecting the applied pressure. In the past, any pressure changes went unnoticed, unknown and/or unaddressed. In various aspects, the present invention allows the attending medical professional(s) to stay informed as to pressure changes, giving the medical professional(s) the capability to re-establish correct pressure by known positive control. As such, various aspects of the present invention bring true reproducible scientific and mechanically responsible practice to the installation of an artificial patella prosthesis in total and partial knee arthroplasty. It will be appreciated that the various aspects of the device and methods described herein are not necessarily limited to applying measured pressure to a patella construct, but may be equally employed in other medical and mechanical applications.
The present invention, in part, brings scientific and mechanical enabling to the surgeon to help create reproducible and successful outcomes. Aspects and embodiments of the current inventive device receive the everted patella in its prepared form whereupon the anterior portion of the natural patella is placed upon a spiked platform of a bottom plate associated with the device. Upon the patella being held in place, the surgeon or other medical professional takes hold of the knob of the knob assembly of the present device, holding it firmly in one hand. With the other hand, the medical professional depresses the quick release button of the present device, freeing the adjustment rod thereupon. As the medical professional pushes downward atop the knob, the indicating assembly of the present device translates downward in a controlled linear direction as its slide ring houses and translates upon the keyed guide rod acting as an established vertical stable construct. When the patella bushing of the present device makes contact with the artificial patella of the patella construct, the medical professional releases the quick release button allowing the adjustment rod threads to functionally engage. The medical professional, with hand upon the assembly knob, turns the knob (e.g., in a clockwise motion), creating a controlled linear downward movement of the indicating assembly generating pressure upon the patella construct. In aspects of the present invention, every clockwise revolution of the knob creates an increase of pressure upon the patella construct. As the controlled pressure is applied, the indicating assembly measures the pressure being applied and an assembly contained calibrated indicator gives visual knowledge and reference as to the precise amount of measured applied pressure being applied.
In alternative embodiments, a medical professional secures an appropriately sized insert into the device, ensures that the everted patella is appropriately situated in the receiving area of the device, adjusts a knob assembly to a desired level associated with a measured pressure.
Upon the surgeon creating the specific required and known applied pressure, the clockwise turning motion upon the assembly knob can be terminated. At this time, the bonding agent within the patella construct will squeegee out; the bottom platform spikes will depress into the anterior patella and the bushing (e.g., a rubber bushing or of other material and design) in the stem of the clamp indicating assembly can settle in. It will be appreciated that the above processes can take effect within seconds and the amount of applied pressure can thereafter decrease.
Thereupon, the present inventive device indicator visually informs the medical professional(s) of the potential adverse change in pressure and this calibrated reference gives the necessary information to correct and re-establish proper pressure. In the event of change from optimum applied pressure, the medical professional can create additional needed known applied pressure by again turning the assembly knob to re-establish the precise prescribed pressure to be upon the patella construct. The present invention thus, in part, enables the medical professional to create and maintain measured applied pressure upon the patella construct until the bone cement is fully cured. Upon the professional confirming the bone cement is fully cured, the present device can be removed by turning the knob in the opposite direction from the direction used to apply pressure, thereby relieving pressure off the indicating device. At such time, the quick release button can be depressed in one embodiment of the present invention, disengaging the assembly rod whereupon the assembly knob can be pulled upward. In this way, the indicating assembly can be quickly advanced up the guide rod to its highest allowable level, after which time the quick release button can be released, whereupon the assembly re-engages the threads of the assembly rod, locking the indicating assembly in place and allowing the removal of the device. In alternative embodiments, no quick release button is employed, and the knob is simply turned sufficiently enough to allow the cured construct to be removed from the device.
Among other things, the present invention revolutionizes the typical known procedure in the installation of an artificial patella prosthetic replacement in total knee arthroplasty and is also introductory to additional improvements within a system of surgical instrumentation.